JP6546881B2 - Position detection device and actuator - Google Patents

Description

  The present invention relates to a position detection device for detecting the position of a reciprocating member and an actuator provided with the position detection device.

  An actuator is used to drive a driven member such as a workpiece or a jig, and the actuator is also used to open and close a hand using the hand holding a workpiece or the like as a driven member. The actuator has a reciprocating member driven by air pressure or liquid pressure, and the reciprocating member is connected to the driven member. In such an actuator, a magnet is attached to the reciprocating member, and a sensor head provided with a magnetoresistive element for detecting the magnetic field of the magnet is attached to the actuator body. Thus, the position of the reciprocating member can be detected based on the output signal of the magnetoresistive element.

  Patent Document 1 discloses a magnetic linear measurement device in which magnetoresistive elements are provided at two places in a sensor head. The two magnetoresistive elements are provided at mutually offset positions in the moving direction of the piston. In this magnetic linear measuring device, the position of the piston is detected when the magnet reaches a position between the two magnetoresistive elements by the movement of the piston which is a reciprocating member. Further, Patent Document 2 discloses a position detection device that includes two magnetoresistive elements arranged in directions orthogonal to each other and detects a piston position of a fluid pressure cylinder. In this position detection device, the temperature compensation circuit compensates for the change in the output voltage from the magnetoresistive element due to the change in the ambient temperature. Further, Patent Document 3 discloses a position detection device in which an LED which is turned on according to the position of a moving member is provided on a sensor head provided in an actuator body. The magnetic sensor of this position detection device has two magnetoresistive bridge circuits each consisting of four magnetoresistive elements, and each of the magnetoresistive bridge circuits outputs an output signal having a phase difference in the moving direction of the magnet .

JP, 2009-128301, A Unexamined-Japanese-Patent No. 11-303818 gazette JP, 2010-48698, A

  If two magnetoresistive elements are provided at two different positions in the moving direction of the reciprocating member as in Patent Document 1, the position can be detected only when the reciprocating member moves between the magnetoresistive elements. When the moving member moves out of the space, the position can not be specified. Moreover, in patent document 2, when the middle point voltage of two magnetoresistive elements becomes the range of two large and small reference voltages, it is made to output an ON signal, and a reciprocation member is located in the range which exists The position of the reciprocating member can not be specified linearly. Furthermore, in Patent Document 3, the position of the reciprocating member is calculated based on the output voltages from the two magnetoresistive bridge circuits, and the position of the reciprocating member can be detected with high accuracy. The range that can be done is limited.

  An object of the present invention is to provide a position detection device capable of detecting the position of a magnet provided on a reciprocating member in a long distance range.

  A position detection device according to the present invention is a position detection device for detecting the position of a magnet moving in a magnetization direction, and a magnetoresistive element having maximum sensitivity to a magnetic field in a first direction which is the magnetization direction, and the first direction And a first bridge circuit outputting a SIN signal, and a magnetoresistive element having a maximum sensitivity in a third direction inclined 45 degrees with respect to the first direction. Element, and a second bridge circuit for outputting a COS signal, and an output signal corresponding to the direction of the magnetic field, the element including the magnetoresistive element having the maximum sensitivity in the fourth direction orthogonal to the third direction, and the maximum sensitivity direction The magnetic field direction detection sensor disposed along the second direction and the binary area discrimination signal corresponding to the polarity of the output voltage of the magnetic field direction detection sensor And region determining means for determining whether the center of the second bridge circuit is located in the region on one side in the moving direction or the region on the other side in the moving direction, the SIN signal, and the COS The ATAN binary arithmetic unit calculates the ATAN2 value based on the signal, and the position arithmetic unit calculates the position of the magnet based on the area discrimination signal and the ATAN2 value, and the area discrimination signal A position at which switching is performed later than the peak position of the SIN signal is a region switching point, and a value whose absolute value is larger than the absolute value of the ATAN2 value corresponding to the region switching point is a region switching threshold. The absolute value of the ATAN2 value Is larger than the area switching threshold value, the position calculation unit determines the area according to the area determination signal, calculates the position of the magnet, and the absolute value of the ATAN2 value is the value When less than frequency switching threshold, the position calculation unit calculates the position of the magnet regardless of the region determination signal.

  The bridge circuit of two magnetoresistive elements whose maximum sensitivity directions are different by 45 degrees respectively outputs a SIN signal and a COS signal. The ATAN2 value is calculated from the two signals. The output voltage of the magnetic field direction detection sensor is used to determine whether the magnet is positioned in the axial direction one side or in the other side with respect to the central portion of the first bridge circuit and the second bridge circuit. Ru. Based on the ATAN2 value and the area discrimination signal, the ATAN2 value is divided into the main area value and the shift area value, and shift processing is performed, and a signal corresponding to the position of the magnet is output. The area discrimination signal switches later than the peak position of the SIN signal. A value whose absolute value is larger than the value of the ATAN2 value at the position of the switching point, that is, the area switching point is taken as a switching threshold. When the absolute value of the ATAN2 value is smaller than the area switching threshold value, the position of the magnet is calculated regardless of the area determination signal, so that the position detection accuracy can be enhanced. Thereby, the position of the magnet provided in the reciprocating member can be detected with high accuracy in a long distance range.

It is a longitudinal cross-sectional view which shows the actuator in which the position detection apparatus was provided. It is a top view of FIG. It is a top view which shows the pattern of a magnetoresistive element. (A) is a circuit diagram showing a first bridge circuit in which parts of the magnetoresistive element patterns shown in FIG. 3 are connected to each other, and (B) is a part of the magnetoresistive element patterns shown in FIG. 3 Are connected to each other, and are a circuit diagram showing a second bridge circuit. (A)-(C) are schematic which shows the magnetic field of a magnet, and the sensitivity direction of a Hall element. It is a block diagram of a position detection device. It is a graph which shows an example of an internal signal and a calculated value of a position sensing device corresponding to a magnet position, (A) shows SIN signal and COS signal outputted from a magnetoresistive bridge circuit, (B) shows a SIN signal The sum of the absolute value and the absolute value of the COS signal is shown, (C) shows the area discrimination signal based on the output voltage of the Hall element, and (D) shows the ATAN2 value obtained based on the SIN signal and the COS signal. (E) shows an enlarged output signal in which the shift area value is added to the main area value. It is an enlarged view which shows the principal part of FIG. It is a block diagram of the position detection apparatus which is a modification. FIG. 7 is a characteristic diagram showing an output waveform of a proximity sensor for detecting an area distinguishable range. (A)-(E) are schematic which shows the magnetic field of a magnet, and the sensitivity direction of a magnetic sensor. It is a block diagram of a position detection apparatus which has a magnetic sensor shown in FIG. It is sectional drawing which shows the modification of the actuator in which a position detection apparatus is provided.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The actuator 10 shown in FIGS. 1 and 2 has a cylinder 11 as an actuator body. A piston 12 as a reciprocating member is axially reciprocably mounted in the cylinder 11. The cylinder 11 and the piston 12 are formed of a nonmagnetic material such as an aluminum alloy, and the piston rod 13 is provided on the piston 12. When compressed air is supplied from the port 14 a to the pressure chamber 14 of the cylinder 11, the piston rod 13 is driven in a direction to protrude from the cylinder 11. On the other hand, when compressed air is supplied from the port 15 a to the pressure chamber 15 of the cylinder 11, the piston rod 13 is driven in the direction to retract into the cylinder 11. In the piston 12, the end face from which the piston rod 13 protrudes is the rod side, and the opposite side is the head side.

  An annular magnet 16 is provided on the piston 12. The magnet 16 is mounted in an annular groove provided on the outer peripheral surface of the piston 12. The magnet 16 is magnetized in the moving direction of the piston 12 and moves in the magnetization direction by the piston 12. The magnet 16 has, for example, an S pole on the rod side and an N pole on the head side, and a magnetic field indicated by symbol H in FIG. 1 is generated by the magnet 16.

  A sensor head 21 is mounted on the cylinder 11 in order to detect the axial position of the magnet 16 relative to the cylinder 11. When the axial position of the magnet 16 is detected, the axial position of the piston 12 can be detected. A printed wiring board 22 is provided inside the sensor head 21. The printed wiring board 22 is provided radially outward of the piston 12. That is, the printed wiring board 22 is provided perpendicularly to the cylinder 11. Further, the printed wiring board 22 extends along the reciprocating direction of the piston 12. The printed wiring board 22 has component mounting surfaces 23 and 24 on both front and back surfaces, the magnetoresistive bridge circuit 25 is mounted on one of the component mounting surfaces 23, and the Hall element 26 is on the other component mounting surface 24 as a magnetic field direction detection sensor. Will be mounted.

  FIG. 3 is a plan view showing a pattern of the magnetoresistive bridge circuit 25. As shown in FIG. FIG. 4A shows a first bridge circuit 31 in which a bridge circuit is formed by mutually connecting R1, R2, R3 and R4 among the magnetoresistance elements shown in FIG. FIG. 4B shows a second bridge circuit 32 in which the bridge circuit is formed by mutually connecting R5, R6, R7, and R8 among the magnetoresistance elements shown in FIG.

  The magnetoresistive element pattern is formed into a film of a magnetoresistive material on the substrate layer 27 and then patterned into a predetermined shape using a fine processing technique. The respective magnetoresistive element patterns are formed in a meander shape by alternately connecting a long strip-shaped pattern and a short strip-shaped pattern at right angles. In each of the magnetoresistive elements, the change in the resistance value is the largest with respect to the change in the magnetic field applied in the direction orthogonal to the long strip-like pattern, and has the maximum sensitivity. On the other hand, the change in the resistance value is the smallest with respect to the change in the magnetic field applied in the direction along the long strip pattern.

  In the first bridge circuit 31, as shown in FIG. 4A, assuming that the direction of the applied magnetic field is the first direction M1, the first magnetoresistance element R1 has maximum sensitivity to the magnetic field in the first direction M1. Have. On the other hand, the second magnetoresistance element R2 has maximum sensitivity to the magnetic field in the second direction M2 orthogonal to the first direction M1. Similarly, the third magnetoresistance element R3 has maximum sensitivity to the magnetic field in the first direction M1, and the fourth magnetoresistance element R4 has maximum sensitivity to the magnetic field in the second direction M2.

  The first magnetoresistance element R1 and the fourth magnetoresistance element R4 are connected in series by the wiring pattern 35b to form a first half bridge 31a which is a first circuit pattern. The second magnetoresistance element R2 and the third magnetoresistance element R3 are connected in series by the wiring pattern 35a to form a second half bridge 31b which is a second circuit pattern.

  The power supply voltage Vcc is applied to the connection end 34a of the wiring pattern 33a, and the connection end 34b of the wiring pattern 33b is connected to the ground Gnd. Output voltages A and B are taken out from the connection ends 36a and 36b of the respective wiring patterns 35a and 35b. Thus, the first bridge circuit 31 is a full bridge circuit provided with four magnetoresistance elements.

  In the second bridge circuit 32, as shown in FIG. 4B, the fifth magnetoresistance element R5 has the maximum sensitivity to the magnetic field in the third direction M3 inclined 45 degrees with respect to the first direction M1. On the other hand, the sixth magnetoresistance element R6 has the maximum sensitivity to the magnetic field in the fourth direction M4 orthogonal to the third direction M3. Similarly, the seventh magnetoresistance element R7 has maximum sensitivity to the magnetic field in the third direction M3, and the eighth magnetoresistance element R8 has maximum sensitivity to the magnetic field in the fourth direction M4.

  The fifth magnetoresistive element R5 and the eighth magnetoresistive element R8 are connected in series by the wiring pattern 39b to form a third half bridge 32a which is a third circuit pattern. The sixth magnetoresistance element R6 and the seventh magnetoresistance element R7 are connected in series by the wiring pattern 39a to form a fourth half bridge 32b which is a fourth circuit pattern.

  The power supply voltage Vcc is applied to the connection end 38a of the wiring pattern 37a, and the connection end 38b of the wiring pattern 37b is connected to the ground Gnd. Output voltages C and D are taken out from the connection ends 40a and 40b of the respective wiring patterns 39a and 39b. Thus, the second bridge circuit 32 is a full bridge circuit including four magnetoresistance elements.

  As shown in FIG. 3, the magnetoresistive element patterns constituting the eight magnetoresistive elements R <b> 1 to R <b> 8 are formed in the same substrate layer 27. Assuming that the central portion of the first bridge circuit 31 formed of the magnetoresistive elements R1 to R4 is O, the second bridge circuit 32 formed of the magnetoresistive elements R5 to R8 is a first bridge circuit centered on the central portion O. It is inclined 45 degrees to 31. As described above, in the magnetoresistive bridge circuit 25, eight magnetoresistive elements R 1 to R 8 forming the first bridge circuit 31 and the second bridge circuit 32 are placed on the substrate layer 27 at 45 ° intervals around the central portion O. It is formed.

  The magnetoresistive bridge circuit 25 is mounted on the component mounting surface 23 of the printed wiring board 22 as shown in FIG. The magnetic field applied to the magnetoresistive bridge circuit 25 differs depending on the position of the piston 12. When the piston 12 moves, the first bridge circuit 31 outputs a first output signal, that is, a SIN signal (sine signal) according to the change in the direction and the strength of the magnetic field applied to the magnetoresistive elements R1 to R4. On the other hand, the second bridge circuit 32 generates a second output signal different in phase in the moving direction of the piston with respect to the SIN signal according to the change in the direction and the strength of the magnetic field applied to the magnetoresistive elements R5 to R8, that is, COS Output a signal (cosine signal). In this specification, the first output signal which is the output of the first bridge circuit 31 is referred to as the SIN signal for convenience, and the second output signal which is the output of the second bridge circuit 32 is referred to as the COS signal for convenience. Since neither the first output signal nor the second output signal is a repetitive signal, the definitions of SIN and COS do not apply correctly, but are referred to as such for convenience.

  Based on the SIN signal and the COS signal, an ATAN2 value, that is, an arctangent value is calculated. In this specification, the arctangent value is referred to as an ATAN2 value.

  Such ATAN2 values have a plurality of values with respect to the axial position of the magnet 16. Therefore, the axial position of the magnet 16 can not be identified from only the ATAN2 value. However, for example, if the axial length is very short, it is possible to specify the axial position of the magnet 16 from the ATAN2 value, but the range in which the axial position of the magnet 16 can be specified is about 2 mm to 7 mm Limited to the range of strokes. This range depends on the strength and size of the magnet and the distance between the sensor head and the magnet.

  Then, the range which specifies the axial direction position of the magnet 16 using a magnetic sensor can be expanded as follows. That is, whether the magnet 16 is located on one side of the central portion O of the magnetoresistive bridge circuit 25, ie, on the rod cap side, or on the other side, ie, on the head cap side. Can be determined based on the output signal of the magnetic sensor. The details thereof will be described later with reference to FIG. 7 and the description thereof by taking the Hall element 26 as an example. However, the magnetic sensor is not limited to the Hall element, and any sensor having a function of detecting the direction of the magnetic field, that is, a magnetic field direction detection sensor may be used.

  As shown in FIG. 2, the magnetoresistive bridge circuit 25 is mounted on the component mounting surface 23 of the printed wiring board 22, whereas the Hall element 26 as an example of the magnetic field direction detection sensor is on the opposite component mounting surface 24. Will be mounted on. The Hall element 26 is disposed at the position of the vertical direction line U perpendicular to the central portion O of the magnetoresistive bridge circuit 25. Therefore, Hall element 26 is arranged at a position different in the direction of circumferential line U with respect to magnetoresistive bridge circuit 25 by the thickness dimension of printed wiring board 22, and the center of magnetoresistive bridge circuit 25 in the moving direction of magnet 16. Placed in part O. That is, although the Hall element 26 and the magnetoresistive bridge circuit 25 are arranged at different positions in the circumferential direction of the cylinder 11, the Hall element 26 and the magnetoresistive bridge circuit 25 are in the moving direction of the piston rod 13. It is arranged at the same position.

  FIG. 5 is a schematic view showing the polarity of the Hall voltage, that is, the output voltage of the Hall element, according to the position of the magnet and the Hall element.

  When the axially moving magnet 16 approaches the Hall element 26, a magnetic field H is applied to the Hall element 26. The magnetic field H is divided into two components: the magnetic field strength (Hz) of the horizontal component which is the moving direction of the magnet 16 and the magnetic field strength (Hr) of the vertical component which is the direction perpendicular to the moving direction. The Hall element 26 has the minimum sensitivity in the moving direction of the magnet 16, ie, the first direction M1, and has the maximum sensitivity to the magnetic field in the direction perpendicular to the axial direction, ie, the second direction M2. The output of the Hall element 26 is input to the comparator 28. The output of the comparator 28 is a binary value of High or Low, and based on the value, is the position of the magnet 16 positioned on one side in the axial direction with respect to the central portion O or on the other side? To determine

As described above, two values corresponding to the polarity of the output voltage of the Hall element 26 are defined as the area determination signal. When the output voltage of the Hall element 26 is input to the comparator 28, the area determination signal is a binary signal of High or Low, which is the output of the comparator 28. The comparator 28 is an example of an area determination unit that generates an area determination signal from the output voltage of the Hall element.
As shown in FIG. 5A, when the magnet 16 is positioned on the left side (head cap side) with respect to the Hall element 26, the magnetic field H has a component directed from the upper surface to the lower surface of the Hall element 26 in the figure. That is, since the component Hr of the magnetic field H is in the negative direction, the output terminal voltage of the Hall element 26 has, for example, a negative polarity, and the output of the comparator 28 has, for example, High. As shown in FIG. 5C, when the magnet 16 is positioned on the right side (the rod cap side) with respect to the Hall element 26, the magnetic field H has a component directed from the bottom to the top of the Hall element 26 in the figure. That is, since the component Hr of the magnetic field is in the positive direction, the output terminal voltage of the Hall element 26 has, for example, the positive polarity contrary to FIG. 5A and the output of the comparator 28 has, for example, Low as in FIG. It becomes. The polarity of the output terminal voltage of the Hall element 26 is switched when the magnet 16 moves and is located at the same position as the Hall element 26 in the axial direction. That is, with the position as a boundary, the polarity of the output terminal voltage of the Hall element 26 is reversed, and the output of the comparator 28 is also reversed. FIG. 5B shows a situation where the magnet 16 is located at such a boundary position.

  As described above, the polarity of the output terminal voltage of the Hall element 26 determines whether the position of the magnet 16 is a region on one side in the axial direction or the other side with respect to the central portion O of the magnetoresistive bridge circuit 25. It can be determined.

  However, since the minimum detection sensitivity of the Hall element 26 is, for example, about 15 Gauss as the component Hr of the magnetic field, the output of the comparator 28 is not switched in a magnetic field smaller than that. When the component Hr of the magnetic field becomes about 15 Gauss or more, the polarity of the output terminal voltage of the Hall element 26 is switched, and the output of the comparator 28 is switched. Therefore, the peak position M of the SIN signal by the magnetoresistive element is different from the position at which the output of the comparator 28 switches, that is, the positive region switching point J1 and the negative region switching point J2.

  FIG. 6 is a block diagram of a position detection device. The output voltages A and B of the first bridge circuit 31 are input to the amplifier 41, and the output voltages C and D of the second bridge circuit 32 are input to the amplifier. The first output signal, ie, the SIN signal, which is the output of the amplifier 41, and the second output signal, ie, the COS signal, which is the output of the amplifier 42, are sent to the ATAN2 value calculator 43. The ATAN binary value calculator 43 as the ATAN binary value calculator calculates the ATAN2 value based on the SIN signal and the COS signal, and outputs a value corresponding to the ATAN2 value to the position calculator. In order to obtain the ATAN2 value from the SIN signal and the COS signal, the ATAN2 value calculation unit 43 can be provided separately from the position calculation unit 44 as described above, but the ATAN2 value can also be obtained by a program.

  The output of the comparator 28, which is the ATAN2 value and the area discrimination signal, is sent to the position calculation unit 44.

  The axial position of the magnet 16 calculated by the position calculation unit 44 is displayed on the numerical display unit 45 as a numerical value. An indicator 46 made of an LED is provided on the printed wiring board 22 of the sensor head 21. The indicator 46 is controlled to be turned on by the ON / OFF determination unit 47 based on a signal from the position calculation unit 44, and is turned on when the piston 12 is positioned within a predetermined range.

  The position calculation unit 44 outputs an analog signal corresponding to the axial position of the magnet 16 to the analog output terminal 50 through the D / A conversion unit 48 and the buffer 49. The position calculation unit 44 outputs a position signal to the first output terminal 51 to the fourth output terminal 54 via the output determination and driver circuit 55. The set value is input from the numerical value setting unit 56 to the output determination unit / driver circuit 55. By operating the numerical value setting unit 56, a detection position at which the first output end 51 to the fourth output end 54 are turned on / off, that is, a set value is input. When the detection position of the magnet 16 is set by the numerical value setting unit 56, when the magnet 16 reaches the set position, the respective output ends 51 to 54 output ON signals to the external device. The detection position of the magnet 16 can be set to four places by the numerical value setting unit 56. Based on the signal from the analog output terminal 50, a number of positions can be detected by an external circuit.

  FIG. 7 is a graph showing an example of a signal for calculating the position of the magnet 16 in the position detection device, and FIG. 8 is an enlarged view showing the main part of FIG.

  In FIG. 7, a piston 12 provided with a magnet 16 and a region discrimination signal corresponding to the SIN signal and the COS signal of the magnetoresistive bridge circuit 25 and the polarity of the Hall voltage of the Hall element 26 and the value calculated from those signals. It has been shown to change depending on the position of. As described above, the first bridge circuit 31 outputs the SIN signal, and the second bridge circuit 32 outputs the COS signal whose phase is different from that of the SIN signal. The voltage of each signal output is offset so as to be 0 V when there is no magnetic field, and amplified by the amplifiers 41 and 42 such that the maximum amplitude of the output voltage is in the range of 1 V to -1 V.

  FIG. 7A shows a SIN signal and a COS signal after amplification. When the magnet 16 is far from the sensor head 21 in the axial direction, the magnetic field applied to the first bridge circuit 31 and the second bridge circuit 32 is low. As a result, the rate of change of the SIN signal and the COS signal with respect to the change of the position of the magnet 16 is low. As shown in the vicinity of the horizontal axis 40 to 80 in FIG. 7A, as the magnet 16 approaches the sensor head 21, the magnetic field increases and the change in the direction of the magnetic field relative to the change in the position of the magnet 16 also increases. Accordingly, the resistance value of the magnetoresistive element also changes significantly, and the rate of change of the SIN signal and the COS signal also increases.

  FIG. 7B shows the addition value (| SIN | + | COS |) of the absolute value of the SIN signal and the absolute value of the COS signal, and the addition value is calculated by the position calculation unit 44. FIG. 7C shows an area discrimination signal obtained by the Hall element 26. FIG.

  When the magnet 16 approaches the sensor head 21, the added value shown in FIG. 7B is increased, and a magnetic field of an intensity that can determine the area is applied to the Hall element 26 as well. Conversely, when the magnet 16 is separated from the sensor head 21 and the added value shown in FIG. 7B is small, the magnetic field applied to the Hall element 26 is also small, and the output of the comparator 28 is the output of the Hall element 26. Since it may not correspond, it can not be determined using the area determination signal.

  This occurs in the following cases. When the magnet 16 is separated from the sensor head 21, the output signal of the comparator 28 immediately after the power is turned on, that is, the area discrimination signal, is the position of the magnet 16 positioned on one side in the axial direction with respect to the central portion O? It may not correspond to whether it is located on the other side. That is, the area determination signal immediately after power on is indeterminate. However, once the piston 12 has moved from end to end, the output of the comparator 28 is latched, so that the area discrimination signal is positioned so that the position of the magnet 16 is on one side in the axial direction with respect to the central portion O. Corresponds to whether it is located on the other side. As described above, in response to the area determination signal immediately after power on being undetermined, the area determination signal is adopted while being limited to the range of the area determination range E.

  Thus, the output of the comparator 28 is adopted only in the region where the output of the comparator 28 corresponds to one side in the axial direction or the other side in the axial direction of the central portion O, that is, the region distinguishable range E of FIG. . Thus, it can be determined from the output of the comparator 28 whether the position of the magnet 16 is positioned on one side in the axial direction with respect to the central portion O or on the other side. The area discriminable threshold value X for discriminating the area discriminable range E from the sum of the absolute value of the SIN signal and the absolute value of the COS signal is a practically appropriate value so that a stable area discrimination signal can be selected. It is determined.

  If the area discriminable threshold value X is set to a value too low, as understood from FIGS. 7B and 7C, the area discriminable range E becomes wider than the range in which the area discrimination signal is effective. It will Then, the region discrimination signal is used including the region to the left of the point F in FIG. 7C, that is, the region which can not be used, which is disadvantageous. The area discriminable threshold value X is set to a practically appropriate value so that such a disadvantage does not occur.

  The polarity of the output voltage of the Hall element 26 is stable in the area on the right side of the F position in FIG. 7C, but the value is determined as an area higher than the added value (| SIN | + | COS |) at the F position By setting as the possible threshold value X, a region in which the polarity of the output voltage of the Hall element 26 is more stable can be used. As described above, the value of High or Low corresponding to the polarity of the output voltage of the Hall element 26, that is, the area discrimination signal is adopted within the range of the area discriminable range E, and is not adopted in the other ranges. Not adopting this means that the position calculation unit 44 does not calculate the position of the magnet 16 and does not output a signal corresponding to the position of the magnet 16.

  The position where the area discrimination signal indicating whether the position of the magnet 16 is located in the area on one side or the area on the other side with respect to the central portion O of the magnetoresistive bridge circuit 25 changes as shown in FIG. It is a position of area | region switching point J1, J2 shown to C). When the magnet 16 moves from left to right in FIG. 7, the area discrimination signal switches at the area switching point J1. When the magnet 16 moves from right to left in FIG. 7, the area discrimination signal switches at the area switching point J2. Thus, when the magnet 16 moves, the area discrimination signal switches after passing the peak position of the SIN signal, that is, behind the peak position of the SIN signal.

  The Hall element 26 is located at the same position as the central portion O of the magnetoresistive bridge circuit 25 in the moving direction of the magnet 16, but the area switching points J1 and J2 at which the polarity of the output signal of the Hall element 26 switches With respect to the position of the peak voltage value of the SIN signal, as described above, positioned slightly closer to the head cap or rod cap. As described above, this “difference in position” is the length L between the area switching points J1 and J2 around the position of the peak voltage value of the SIN signal due to the minimum detection sensitivity of the Hall element 26. Hysteresis occurs.

  FIG. 7D shows ATAN2 values obtained based on the SIN signal and the COS signal.

  As described above, the peak position M of the SIN signal by the magnetoresistive element and the area switching points J1 and J2 at which the output of the comparator 28 switches are different due to the minimum detection sensitivity of the hall element 26. For example, assuming that a value slightly larger than the ATAN2 value corresponding to the area switching point J1 is the plus side area switching threshold value g shown in FIG. 7D, the value of ATAN2 value shown in FIG. A value substantially symmetrical to the side area switching threshold value g is set as the minus side area switching threshold value f. Alternatively, assuming that a value slightly smaller than the ATAN2 value corresponding to the area switching point J2 is the minus side area switching threshold value f shown in FIG. 7D, the ATAN2 value shown in FIG. A value substantially symmetrical to the side area switching threshold f is set as a plus side area switching threshold g. In any case, the plus side area switching threshold g and the minus side area switching threshold f have different signs. In terms of magnitude, −π <f <0 <g <+ π. The plus side region switching threshold g and the minus side region switching threshold f may have the same absolute value, but they may not be the same. The area switching points J1 and J2 are included in axial positions corresponding to the ATAN2 value between the minus area switching threshold f and the plus area switching threshold g.

  As described above, when the plus side region switching threshold value g is determined from the minus side region switching threshold value f, it is determined whether the position of the magnet 16 is located on one side or the other side from the center of the magnetoresistive bridge circuit 25 An area discrimination signal based on the output of the comparator 28 of the Hall element 26 can be used for discrimination. Alternatively, even if the minus side region switching threshold f is determined from the plus side region switching threshold g, the same effect is obtained.

  Here, the relationship between the area distinguishable range E, the minus side area switching threshold f, and the plus side area switching threshold g will be described below, centering on the area discrimination signal. In the range discriminable range E obtained from the addition value of the absolute value of the SIN signal and the absolute value of the COS signal, except when the ATAN2 value is in the range from the minus side region switching threshold f to the plus side region switching threshold g The area discrimination signal is employed. Outside the range of the area discriminable range E, the area discrimination signal is not adopted. Also, even when the ATAN2 value is from the minus side region switching threshold f to the plus side region switching threshold g, the region discrimination signal is not adopted. Since the area discrimination signal is used limited to such a range, a fault that the output signal of the comparator 28 immediately after power on is indeterminate, the position of the peak position M of the SIN signal and the area switching points J1 and J2 Two obstacles are avoided, one of which is the difference between the two.

  Assuming that a value smaller than the ATAN2 value corresponding to the area switching point J1 is the plus side area switching threshold value g shown in FIG. 7D, the area switching point J1 switches from the minus side area switching threshold f to the plus side area It is not included in the axial position corresponding to the ATAN2 value between the thresholds g. That is, the output of the comparator 28 of the Hall element 26 is switched at a position outside the axial position corresponding to the ATAN2 value between the minus side region switching threshold f and the plus side region switching threshold g. Therefore, the area determination signal can not be used to determine whether the position of the magnet 16 is located on one side or the other side of the center of the magnetoresistive bridge circuit 25. For this reason, a value slightly larger than the ATAN2 value corresponding to the area switching point J1 is set as the plus side area switching threshold value g shown in FIG. 7 (D).

  The aforementioned length L due to the minimum detection sensitivity of the Hall element 26 is desirably smaller and ideally zero. However, since the minimum detection sensitivity of a real Hall element is not zero but has a certain magnitude, in order to avoid this failure, the plus side region switching threshold g and the minus side region switching threshold f are determined as described above .

  The ATAN2 value has a main area value and a shift area value. The main region value is a value in the main region P where the magnet 16 is located near the central portion O of the magnetoresistive bridge circuit 25 and changes continuously in a form close to a linear function. The shift area values are values in shift areas K1 and K2 outside the main area P. The ATAN2 value in the main region P takes continuous values from -.pi. To + .pi., And changes substantially linearly in the range corresponding to the axial position of the magnet 16. When the magnet 16 moves from the shift area K1 to the main area P, the ATAN2 value changes discontinuously from + π to −π at the turnaround point a. On the other hand, when the magnet 16 passes the turning point b and moves from the main area P to the shift area K2, the ATAN2 value changes discontinuously from + π to −π.

  Based on the area discriminable range E determined based on the area discriminable threshold value X in FIG. 7B and the area discrimination signals High and Low shown in FIG. 7C within the area discriminable range E , ATAN2 values are manipulated as shown in FIG. 7 (D) to obtain the final result of FIG. 7 (E). The procedure is as follows.

  If the ATAN2 value is between the minus side region switching threshold f and the plus side region switching threshold g within the region distinguishable range E of FIG. 7B, the position of the magnet 16 can be specified. The ATAN2 value is output from the position calculation unit 44 as it is. That is, in the range of the range discriminable range E, if the ATAN2 value is between the minus side region switching threshold f and the plus side region switching threshold g, the position of the magnet 16 and the ATAN2 value correspond one to one. . It corresponds to the section U of FIG. 7 (E).

  In the ATAN 2 value, one value between the plus side region switching threshold value g and π is set as the plus side shift threshold value h. Similarly, in the ATAN 2 value, one value between −π and the minus area switching threshold f is set as the minus shift threshold e. In terms of magnitude, −π <e <f <0 <g <h <+ π. The absolute values of the positive shift threshold h and the negative shift threshold e may or may not be the same.

  When the area determination signal shown in FIG. 7C is Low and the ATAN2 value is between the negative shift threshold e and the negative shift threshold f, it is determined that the area is an undetectable area. The ATAN2 value is not adopted. When the area determination signal is High and the ATAN2 value is between the minus shift threshold e and the minus area switching threshold f, it is determined that the area is a detectable area, and the ATAN2 value is adopted. The adopted ATAN2 value is output from the position calculation unit 44 as it is. At that time, the position of the magnet 16 and the ATAN2 value correspond to one to one. It corresponds to the section T of FIG. 7 (E). Furthermore, when the area determination signal is High and the ATAN2 value is from the negative shift threshold e to -π, it is determined that the area is a detectable area, and the ATAN2 value is adopted. The adopted ATAN2 value is output from the position calculation unit 44 as it is. It corresponds to the section S of FIG. 7 (E).

  When the area determination signal shown in FIG. 7C is High and the ATAN2 value is between the plus area switching threshold g and the plus shift threshold h, it is determined that the area is an undetectable area. The ATAN2 value is not adopted. When the area determination signal is low and the ATAN2 value is between the plus side area switching threshold g and the plus side shift threshold h, it is determined that the area is a detectable area, and the ATAN2 value is adopted. The adopted ATAN2 value is output from the position calculation unit 44 as it is. It corresponds to the section V of FIG. 7 (E). Furthermore, when the area determination signal is low and the ATAN2 value is equal to or more than the plus shift threshold h, it is determined that the area is a detectable area, and the ATAN2 value is adopted. The adopted ATAN2 value is output from the position calculation unit 44 as it is. It corresponds to the section W of FIG. 7 (E).

  As described above, in the sections S, T, U, V, W, the position of the magnet 16 and the ATAN2 value correspond one to one. Therefore, ATAN2 values of the sections S, T, U, V, W can be used as values (or signals) representing the position of the magnet 16.

  When the area determination signal shown in FIG. 7C is Low and the ATAN2 value is equal to or less than the negative shift threshold e, 2π is added to the ATAN2 value, and the result is output from the position calculation unit 44. This corresponds to the range of the shift region K2 in FIG. 7D, and corresponds to the section X in FIG. 7E. The shift area K2 is added to the main area P by this addition (ATAN2 value + 2π). Such addition processing may be referred to as shift processing. When the area determination signal is low and the ATAN2 value is less than or equal to the negative shift threshold e, the ATAN2 value and the position of the magnet 16 correspond one to one. As described above, by using the area discrimination signal based on the output of the Hall element 26, it is possible to add the shift area value of the shift area K2 to the main area value of the main area P and extend the detection range.

  When the area determination signal shown in FIG. 7C is High and the ATAN2 value is greater than or equal to the plus shift threshold h, 2π is subtracted from the ATAN2 value, and the result is output from the position calculation unit 44. This corresponds to the range of the shift region K1 of FIG. 7D, and corresponds to the section R of FIG. 7E. The shift area K1 is added to the main area P by this subtraction (ATAN binary value −2π). Such subtraction processing may be referred to as shift processing. When the area determination signal is High and the ATAN2 value is equal to or greater than the plus shift threshold h, the ATAN2 value and the position of the magnet 16 correspond one to one. As described above, by using the area discrimination signal based on the output of the Hall element 26, it is possible to add the shift area value of the shift area K1 to the main area value of the main area P and extend the detection range.

  As described above, within the range distinguishable range E of FIG. 7B, based on the range determination signal of FIG. 7C, the ATAN2 value of FIG. 7D has threshold values e, f, g, It is divided into a plurality of divisions by h. In particular, by using the ATAN2 value corresponding to the shift areas K1 and K2 in FIG. 7D as an extension of the ATAN2 value in the main area P, the ATAN2 value can be obtained as a continuous value. The detection range can be expanded to obtain an expanded output value of the detection range Q as shown in FIG.

  The conventional detection range was about 2 mm to 7 mm as described above, but in the present invention, the detection range was expanded to be about 10 mm to 25 mm. This range depends on the strength and size of the magnet and the distance between the sensor head and the magnet.

  If the plus side shift threshold value h is set to a value lower than the case shown in the drawing, the detection range Q can be expanded beyond the range shown in FIG. 7 (E). Similarly, the detection range Q can be expanded by setting the negative shift threshold e to a value higher than that shown in the drawing. However, in such a case, in the enlarged shift areas K1 and K2, the rate of change of the ATAN2 value with respect to the change in the position of the magnet 16 becomes smaller, and the resolution of that portion is reduced. Therefore, based on the required specifications, the plus shift threshold h and the minus shift threshold e are set as values that can reduce the position detection error in the detection range Q, that is, according to the resolution that is allowed.

  FIG. 9 is a block diagram of a position detection device according to a modification. In FIG. 6 described above, the ATAN binary value calculation unit 43, the position calculation unit 44, the ON / OFF determination unit 47, and the output determination unit / driver circuit 55 are configured separately. On the other hand, in FIG. 9, the ATAN2 value calculation unit 43, the position calculation unit 44a, the ON / OFF determination unit 47, and the output determination unit 61 are configured by an internal program of the arithmetic processing unit 60 including a CPU. The output judgment unit 61 has a function in the part of the output judgment unit / driver circuit 55 in FIG. 6 excluding the function of the driver circuit. In FIG. 9, the functional configuration of the arithmetic processing unit 60 is shown. Further, if the ATAN binary value calculation unit 43 is configured as an independent IC, the calculation time of the ATAN binary value is shortened, and the overall processing time is shortened.

  As described above, when the addition value (| SIN | + | COS |) of the absolute value of the SIN signal and the absolute value of the COS signal exceeds the region distinguishable threshold value X, as shown in FIG. 7C. Although the embodiment in which the area determination signal is adopted has been described, the addition value (| SIN | + | COS |) may be replaced with the addition value of the square value of the SIN signal and the square value of the COS signal. Furthermore, it is sufficient to calculate from the SIN signal and the COS signal an arithmetic value that increases when the piston 12 having the magnet 16 approaches the sensor head 21 and decreases when it is separated. The addition value with the absolute value of the COS signal (| SIN | + | COS |) or the addition value of the square value of the SIN signal and the square value of the COS signal is merely an example.

  Further, a proximity sensor for detecting the approach of the magnet is added to the magnetoresistive bridge circuit 25 and the Hall element 26 and the sensor head 21 is added, and the area discriminable range E based on the added value (| SIN | + | COS |) The area discriminable range E may be obtained based on the signal of the proximity sensor without obtaining.

  FIG. 10 is a characteristic diagram showing an output waveform of the proximity sensor for detecting the area distinguishable range E. As shown in FIG. As the proximity sensor, one having a circuit configuration provided with a magnetoresistance element as in the first bridge circuit 31 or the second bridge circuit 32 shown in FIG. 4 is used. In the proximity sensor having such a circuit configuration, as shown in FIG. 10, the area discriminable range E can be obtained depending on whether the output of the proximity sensor exceeds the area discriminable threshold value X or not.

  As described above, it is possible to obtain some operation value from the SIN signal and the COS signal of the magnetoresistive bridge circuit 25 or to use a signal from a proximity sensor or the like separately provided in addition to the magnetoresistive bridge circuit 25 and the Hall element 26. The magnet 16 mounted on the piston 12 only needs to be able to detect and judge that the sensor head 21 has approached.

  If it is a sensor that outputs an output signal according to the direction of the magnetic field as the magnetic field direction detection sensor and the maximum sensitivity direction is arranged along the second direction, the magnetic sensor 26a is used instead of the Hall element 26 can do.

  FIGS. 11A to 11E are schematic views showing the sensitivity direction of the magnet of such a magnetic sensor 26a to the magnetic field. FIG. 12 is a block diagram of a position detection device having the magnetic sensor 26a shown in FIG. The magnetic sensor 26a is HGPJPM001A manufactured by Alps Electric Co., Ltd.

  As shown in FIG. 11A, when the magnet 16 is positioned on the left side with respect to the magnetic sensor 26a, the magnetic field H has a component directed from the upper surface to the lower surface of the magnetic sensor 26a. That is, since the component Hr of the magnetic field H is in the negative direction, the output voltage V of the magnetic sensor 26a becomes High as shown in FIG. 11 (D). On the other hand, as shown in FIG. 11C, when the magnet 16 is positioned on the right with respect to the magnetic sensor 26a, the magnetic field H has a component directed from the lower surface to the upper surface of the magnetic sensor 26a. That is, since the component Hr of the magnetic field is in the positive direction, the output voltage V of the Hall element 26 is Low. The output voltage V of the magnetic sensor 26a changes with hysteresis when the magnet 16 moves from the left side to the right side of the magnetic sensor 26a and when the magnet 16 moves in the opposite direction. If the mounting direction of the magnetic sensor 26a is different by 180 degrees, High and Low of the output voltage V are interchanged. Also when the mounting direction of the magnet 16 is reversed, the High and Low of the output voltage V are switched. An internal program can respond to such a change.

  As described above, it is determined from the output voltage of the magnetic sensor 26 a whether the position of the magnet 16 is a region on one side in the axial direction or the other side with respect to the central portion O of the magnetoresistive bridge circuit 25. Can.

  FIG. 1 shows a cylinder 11 provided with a position detection device, but this position detection device is not limited to the cylinder 11, but is also applied to an actuator for opening and closing a hand holding a workpiece etc. can do.

  FIG. 13 is a cross-sectional view showing a modification of the actuator provided with the position detection device. This actuator is an air hand 10a for gripping a workpiece. The air hand 10a has an actuator body 71 made of nonmagnetic material. A piston 12 as a reciprocating member is axially reciprocably mounted inside an actuator body 71, and the piston 12 is provided on a piston rod 13. One end of the piston rod 13 projects into a slit 72 provided at one end of the actuator main body 71, and two L-shaped drive levers 73a and 73b can freely pivot in the slit 72 by fulcrum pins 74a and 74b. It is supported.

  A rod pin 75 is attached to the distal end of the piston rod 13, and the rod pin 75 is slidably engaged with engagement grooves 76a, 76b provided at the proximal end of the respective drive levers. Two sliding levers 77 a and 77 b as fingers for gripping a workpiece or the like are provided at the tip of the actuator body 71. The respective slide levers 77a, 77b are slidable in directions perpendicular to the reciprocation direction of the piston rod 13 by guide rings 78a, 78b attached to the actuator main body 71. A slide pin 79 is provided on the slide lever 77a, and the slide pin 79 is slidably engaged with an engagement groove 81 provided on the tip of the drive lever 73a, and driven by the swing of the drive lever 73a. Similarly, the other slide lever 77b is driven by the swing of the drive lever 73b with a slide pin (not shown) slidably engaged with an engagement groove (not shown) provided at the tip of the drive lever 73b. .

  When the fluid is supplied to the projecting pressure chamber 83 a defined by the cover 82 provided on the actuator body 71 and the piston 12, the piston rod 13 is driven to project. As a result, the two slide levers 77a and 77b are driven to the farthest position via the drive levers 73a and 73b. On the other hand, when the fluid is supplied to the backward pressure chamber 83b, the piston rod 13 is retracted to the position shown in FIG. Thus, the two slide levers 77a and 77b are driven to the closest position via the drive levers 73a and 73b.

  As described above, the workpiece etc. is gripped by the air hand 10a by the gripping operation in which the two sliding levers 77a and 77b move closer, and the workpiece etc. in the opening operation in which the two sliding levers 77a and 77b move apart. The grip is released. The position of the magnet 16 provided on the piston 12 detects the gripping position of the sliding levers 77 a and 77 b. In order to detect the position of the magnet 16, the sensor head 21 shown in FIG.

  As described above, the position detection device described above can be applied to the air hand 10a for driving to open and close the hand holding the workpiece or the like by the reciprocating member.

  In each of the actuators, the position of the magnet 16 corresponds to the position of the reciprocating member such as the piston 12. Depending on the type of actuator, whether to detect the position of the reciprocating member only by the main region value or to detect the position of the reciprocating member by the enlarged output of the detection range Q in which the shift region value is added to the main region value You can also choose.

  In the magnetoresistive bridge circuit 25 shown in FIGS. 3 and 4, the first bridge circuit 31 and the second bridge circuit 32 are each a full bridge circuit, but may be a half bridge circuit.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. For example, although FIG. 1 and FIG. 2 show the actuator 10 which linearly reciprocates a piston rod by air pressure, the present invention is also applied to an actuator which linearly reciprocates a piston rod by fluid pressure other than air pressure such as hydraulic pressure. can do.

DESCRIPTION OF SYMBOLS 10 Actuator 12 Piston 16 Magnet 21 Sensor head 22 Printed wiring board 25 Magnetoresistive bridge circuit 26 Hall element 26a Magnetic sensor 31 1st bridge circuit 31a 1st circuit pattern 31b 2nd circuit pattern 32 2nd bridge circuit 32a 3rd Circuit pattern 32b Fourth circuit pattern 43 ATAN2 value calculation circuit K1 Shift area K2 shift area P main area Q detection range R1 to R8 magnetoresistance element e negative shift threshold h positive shift threshold f negative shift area threshold g positive Region switching threshold x Region discriminable threshold

Claims (10)

A position detection device for detecting the position of a magnet moving in a magnetization direction, comprising:
A magnetoresistive element comprising a magnetoresistive element having maximum sensitivity to a magnetic field in a first direction which is the magnetization direction, and a magnetoresistive element having maximum sensitivity to a magnetic field in a second direction orthogonal to the first direction, and outputting a SIN signal Bridge circuit,
A magnetoresistive element having a maximum sensitivity in a third direction inclined 45 degrees with respect to the first direction, and a magnetoresistive element having a maximum sensitivity in a fourth direction orthogonal to the third direction, and outputting a COS signal; 2 bridge circuit,
A magnetic field direction detection sensor that outputs an output signal according to the direction of the magnetic field and is disposed such that the maximum sensitivity direction is along the second direction;
According to the binary area discrimination signal corresponding to the polarity of the output voltage of the magnetic field direction detection sensor, the magnet is in the area on one side in the moving direction with respect to the central portion of the first bridge circuit and the second bridge circuit. Area determination means for determining whether it is located or in the area on the other side of the movement direction;
An ATAN binary arithmetic unit that calculates an ATAN2 value based on the SIN signal and the COS signal;
And a position calculation unit that calculates the position of the magnet based on the area determination signal and the ATAN2 value.
A position where the area discrimination signal switches later than the peak position of the SIN signal is set as an area switching point, and a value whose absolute value is larger than the absolute value of the ATAN2 value corresponding to the area switching point is set as an area switching threshold. When the absolute value of the ATAN2 value is larger than the area switching threshold, the position calculating unit determines the area by the area determination signal and calculates the position of the magnet, and the absolute value of the ATAN2 value is the area switching threshold. When smaller, the position calculation unit calculates the position of the magnet regardless of the area determination signal.
Position detection device.   The position detection device according to claim 1, wherein the central portions of the first bridge circuit and the second bridge circuit and the magnetic field direction detection sensor are disposed at the same position with respect to the movement direction of the magnet. Position detection device.   The position detection device according to claim 2, further comprising: a printed wiring board having component mounting surfaces provided on both front and back sides, wherein the magnetoresistive element is mounted on one of the component mounting surfaces of the printed wiring board, the printed wiring board The position detection device, wherein the magnetic field direction detection sensor is mounted on the other component mounting surface of   The position detecting device according to claim 1 or 2, wherein the position calculating unit calculates the position of the magnet when the calculated value from the SIN signal and the COS signal exceeds an area determinable threshold value for determining area determinability. Position detection device. The position detection device according to claim 1, further comprising: a proximity sensor that detects that the magnet approaches the central portion, and the position calculation unit detects the proximity of the magnet when the proximity sensor detects the proximity of the magnet. Position detection device that calculates the position of the magnet. In the position detection device according to any one of claims 1 to 4,
The first bridge circuit is
A first circuit pattern comprising a first magnetoresistance element having maximum sensitivity to the magnetic field in the first direction, and a second magnetoresistance element having maximum sensitivity to the magnetic field in the second direction; A full bridge circuit having a third magnetoresistance element having maximum sensitivity to a magnetic field and a second circuit pattern formed of a fourth magnetoresistance element having maximum sensitivity to a magnetic field in the second direction,
The second bridge circuit is
A third circuit pattern comprising a fifth magnetoresistance element having maximum sensitivity to the magnetic field in the third direction, and a sixth magnetoresistance element having maximum sensitivity to the magnetic field in the fourth direction; A position detection device comprising: a seventh magnetoresistive element having maximum sensitivity to a magnetic field; and a fourth circuit pattern including an eighth magnetoresistive element having maximum sensitivity to a magnetic field in the fourth direction .   The position detection device according to any one of claims 1 to 4, wherein the position of the magnet is calculated based on a main region value of the ATAN2 values.   The position detection device according to any one of claims 1 to 4, wherein a shift area value between a shift threshold value in the shift area and a return point of the ATAN 2 value among the ATAN 2 value is a main area of the ATAN 2 value. A position detection device that shifts and adds to values and calculates an enlarged output value to which a shift area value is added.   The position detection device according to any one of claims 1 to 4, wherein the magnetic field direction detection sensor is a Hall element. An actuator for driving a reciprocating member by fluid pressure, comprising:
A magnet provided to the reciprocating member;
The position detection device according to claim 1;
An actuator.

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